In process automation technology, many different sensors are applied for registering process variables. Examples of such sensors are pH-sensors, gas sensors, flow sensors, mass flow sensors, etc. In modern industrial plants, such sensors are often operated under difficult environmental conditions; for example, the sensors are exposed to corrosive chemicals, heat, vibrations, etc.
For connection of these sensors to a superordinated measuring system, it has proved beneficial to couple the sensors via a contactless interface with a cable circuit, which is connected via a cable with a measurement transmitter. The contactless interface can be, for example, an optical interface, a capacitive interface or an inductive interface. Through use of a contactless interface, wear susceptible, electrical contacts are avoided. Since such a sensor module has no openings for electrical contacts, the surface of the sensor module is hermetically sealed. The surface material of the sensor module surrounds the sensor module completely and can be matched to the particular purpose of use, or to the particular corrosive medium.
German patent application 102 18 606 A1 describes a potentiometric sensor. A potentiometric sensor, especially a pH-sensor or a redox sensor, includes: a transducer for registering a potentiometric variable, especially a pH-value or a redox-potential; and an interface for output to a superordinated unit, especially a transmitter, of a signal dependent on the potentiometric variable. In such case, the potentiometric sensor includes a digital data memory, which is connected permanently with the transducer.
In German patent application DE 103 13 639 A1, an electrochemical gas sensor is described. The gas sensor module includes: a transducer for registering a gas concentration; a digital data memory for storing sensor data or process data; and a contactless interface for connection to a superordinated unit for energy supply of the gas sensor module and for data exchange between the gas sensor module and the superordinated unit.